Thermoacoustic heat pumps (sometimes also referred to as thermoacoustic engines) have evoked considerable interest within the last decade, no doubt because of their relative simplicity and lack of moving parts. For example, a typical thermoacoustic heat pump requires but a single moving part in the form of a loud speaker or driver. The remainder of the pump includes a resonator tube, a so-called "stack," a hot side primary heat exchanger and a cold side primary heat exchanger. The loud speaker or driver sets up a standing wave within the resonator tube with the consequence that a gas therein is ideally alternately compressed and expanded adiabatically.
This, in turn, causes heat to be transferred from one end of the stack to the other. Thus, the temperature at one end of the stack will be lower than the temperature at the other end of the stack and through the use of the primary heat exchangers, a heat transfer fluid can be cooled or heated, depending upon the end of the stack at which the heat exchange fluid is flowing.
A number of publications deal with this type of apparatus. See, for example, Los Alamos Science, Number 14, Fall of 1986 and the article therein entitled "The Natural Heat Engine" by John C. Wheatley et al, the details of which are herein incorporated by reference. Also of some interest is a report prepared for the National Aeronautics and Space Administration under Job Order JSC-3P1-068, Contract No. NAS9-17884 to GE Government Services by Dr. Steven Garrett and entitled "Thermoacoustic Life Sciences Refrigerator--A Preliminary Design Study". As pointed out in the latter, a number of technologies employed in the analysis are relatively well understood but the weakest portions deal with the primary and secondary heat exchangers. The author concludes that it is possible to improve efficiency substantially through improvements in the heat exchangers; and the present invention is directed to accomplishing that goal.